935 User here.
I use Training Peaks with my coach, and seeing very intermittent reliability on syncing workouts from TP to Garmin Connect to my 935.
TP and Connect work well ( mostly ). When Connect doesn't sync workout, I can usually "force" it by changing a segment on TP ( like add 30 seconds to an interval ) and it will re-sync.
The latest issue I'm seeing is that every run workout with repeated intervals is syncing with only 1 repeat!!! 
Example, setup a 5 repeats of 3 min fast pace, 2 min easy pace in TP. 935 gets the workout, but shows only a repeat count of only 1, rather than 5.
Getting pretty tired of the lack of software quality from Garmin. Your HW is great, but the software is utter crap. Features work only intermittently, and that makes it very hard to rely on the Garmin as stable part of my training plan.